Nicla Sense Me power supply

I want to use nicla sense me as shield, but not for MKR board. Eslov is not an option.
I want to understand, how can I power nicla sense me from pins headers.
As I understood, BQ25120 is internal voltages stabiliser for everything you can find on the board. So I was trying to supply 3,3v or 5v (from bq25120 both are acceptable) to vin_bq25120 ping, but no luck - board don't starts.
What am I doing wrong?

Thank you in advance

Here's the link to the datasheet

Pages 14 & 15 explain the pin headers.

yep, I've read everything in the datasheet. in addition to pages 14 & 15, page 12 describes internal power tree. but putting voltage to vin, and connecting gnd - doesn't help with starting this board. putting 3.3 to ext ref too. but everything works fine from usb.
that's why i'm asking.

What are you using as the indication of whether the board started or not?

If you are using a sketch to test this, please post it here.

Power (+3,3V or +5V) was connected to vin_bq25120.
I'm using Blink_Nicla example.

#include "Nicla_System.h"

void setup() {

void loop() {

Also i was testing using a much more complicated scetch with serial communication, but no luck. But as I've said earlier, everything works when powered by usb.

Issue solved. Power should be connected in the next way:
+5V to vin_bq25120 - this powers controller and sensors
+3.3V to vddio_ext - this powers level translators to work with 3.3V boards (rpi, jetson nano etc)

I'm glad the problem is solved. Thanks for taking the time to share your findings @focuzz!

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